<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script crossorigin src="https://unpkg.com/react@18/umd/react.development.js"></script>
    <script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script>
    <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
    <style>
        .active
        {
            background-color: red;
        }
    </style>
</head>
<body>
    <div id="root"></div>
    <script type="text/babel">
      class Root extends React.Component{
        constructor()
        {
            super();
            this.state = {
                movies:["星际穿越","盗梦空间","光年之外","一人之下"],
                currentIndex:0
            }
        }

        btnClick(index)
        {
           this.setState({
             currentIndex:index
           })
        }

        render()
        {
            return (
                <div>
                 <ul>
                 {
                    this.state.movies.map((item,index)=>{
                        return <li
                                key = {index}
                                className = {this.state.currentIndex ===index?'active':''} 
                                onClick ={()=>{this.btnClick(index)}}
                                >{item}</li>
                    })
                 }
                </ul>
                </div>
            )
        }
      }
      const root = ReactDOM.createRoot(document.querySelector("#root"));
      root.render(<Root/>);
    </script>
</body>
</html>